5.2 understand the effects on crop yield of increased carbon dioxide and increased temperature in glasshouses

There are 3 limiting factors of photosynthesis, carbon dioxide concentration, temperature and light

intensity. All 3 of these factors can be controlled in glasshouses to increase crop yield.

The increase in heat allows the rate of photosynthesis to increase because there is more kinetic energy.

The temperature will controlled in a glasshouse, to optimum temperature. At optimum temperature

enzymes are at peak activity. If the heat is too high the enzymes will start to denature so it is important

to keep the temperature constant.

Carbon dioxide is a reactant in the process of photosynthesis, so an increase in carbon dioxide

concentration will mean an increase in the rate of reaction. With more reactant, there is more product,

so with more carbon dioxide there is more glucose/ energy produced. *there is a point where the rate of

photosynthesis can’t go any faster*

Since the rate of photosynthesis is increased, the plant produces more energy which can be used for

growth, therefore: an increase in temperature or carbon dioxide concentration in a glasshouse à faster

rate of reaction à more energy à increase in growth à increase in crop yield

5.1 describe how glasshouses and polythene tunnels can be used to increase the yield of certain crops

 Glasshouses and polythene tunnels can be used to grow crops because they increase the rate of

photosynthesis and increase crop yields. Since conditions can be controlled they can provide an

environment that increases efficiency/allows the process to be sped up.

Glasshouses and polythene tunnels allow farmers to manipulate an artificial environment with optimum

conditions. The limiting factors of photosynthesis (carbon dioxide concentration temperature + light

intensity) and plant growth (availability of light + water, temperature and nutrition) can be maintained to

optimum conditions resulting in a greater yield.

Glasshouses and polythene tunnels mimic the greenhouse effect and provide warmth in the growing area

to increase the rate of photosynthesis (optimum temperature).

Glasshouses:

Glasshouses increase yield of crops by protecting plants from the weather and pests. Heaters can be used

to control temperature (provides warmth) and can also control CO₂ levels. Lamps can provide light day

and night, the extended periods of light maximizes photosynthesis and therefore also increases rate of

growth.

-        Greenhouse gas effect increases the temperature inside the glasshouse and allows the enzymes in the plant to work at optimum temperature.

-        Provides shelter against harsh weather e.g. strong storms/wind

-        Prevents water loss through transpiration

-        Constant conditions

-        Can be warmed through the burning of fossil fuels which will also provide carbon dioxide (one of the requirements of photosynthesis)

Polythene tunnels:

Polythene tunnels can provide some protection against the weather and pests, they are cheaper than

glasshouses and cover a greater area of land so more crops can be grown in them. While they provide less

shelter for the plants, they are sometimes preferred over glasshouses because they are adjustable.

4.17 understand the effects of deforestation, including leaching, soil erosion, disturbance of the water cycle and of the balance in atmospheric oxygen and carbon dioxide

 Reasons of deforestation:

-        Creates new space for farming and agriculture

-        Mining

-        Logging to sell wood which can be used as a fuel

-        To create ingredients

-        Make room for houses

Effects of deforestation:

Leaching:

Since the trees provide a protection cover over the soil, when they are removed, the runoff of water carries dissolved nutrients (they are washed) out of the soil and leaves it infertile. The runoff of water can then leach into a lake and cause eutrophication.

Soil erosion:

Tree roots provide stability; they anchor the soil. When they are removed the soil is left vulnerable and wind or water will be able to wash it away . Without the trees to stabilize the soil structure, landslides are more probable.

Disturbance of water cycle:

Trees are an important part of the water cycle, they are able to regulate water quality and pass on water from the soil back into the atmosphere through a process called transpiration. Deforestation causes a disruption of the water cycle

Balance in atmospheric oxygen and carbon dioxide:

Trees take in carbon dioxide and release oxygen when they photosynthesise, after deforestation there is a build up/imbalance of carbon dioxide in the atmosphere, increasing the carbon dioxide concentration, contributing to global warming. When the trees are burnt, there is additional carbon dioxide being released as well.

Deforestation also causes a loss of habitat for species and desertification.